This invention relates generally to entry space vehicles or any other vehicle which is subject to severe aerodynamic heating, and, more particularly to a base vent assembly for utilization in conjunction with such a vehicle in order to relieve the aerodynamic base pressure and to vent pressure buildup from within the interior of the vehicle.
During many high speed flights and more specifically flight which includes entry of space vehicles into the atmosphere the large kinetic energy of entry vehicles is converted to heat by shock waves and air friction as the vehicle passes through the atmosphere. Generally the air surrounding the vehicle is heated to a temperature of many thousands of degrees. To overcome the detrimental effect on such high temperature careful vehicle design can result in more than 99% of this energy remaining in the surrounding air.
During entry into the atmosphere heat is transferred to the vehicle by two mechanisms: convection and radiation. Heating during entry from elliptic flight paths is predominantly convective. At the higher entry speeds characteristic of hyperbolic flight paths, however, the air adjacent the vehicle can become incandescent and radiative energy may become the dominant source of heating. Vehicles having large blunt faces cope most effectively with convective heating, but large-angle conical vehicles have been proposed for the higher speeds, at which radiation becomes a serious problem. Although such vehicles experience more convective heating than blunt-faced ones, their consequent large reductions of radiative heating could significantly reduce overall heating.
The three major means for heat shielding entry space vehicles are heat sinks, mass injection, and reradiation. In instances, however, where the vehicle is subject to severe aerodynamic heating, the vehicle must also be vented. In the past, separate vents have been provided in the vehicle body. These vents usually have been constructed by machining complex parts required because it is desirable that the vents be of a labyrinth type design. Such a design protects the interior of the vehicle from radiant heating and other effects of the hot aerodynamic environment in which the vehicle operates. The major drawbacks associated with individual vents heretofore in use included requirement of dedicated space in the base of the vehicle, great expense in the construction of the vents and the addition of weight to the vehicle which did not contribute to the structural integrity of the vehicle.